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Los fosfatos de los meteoritos muestran una tasa de desintegración constante de 176Lu desde hace 4557 millones de
1Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada. yamelin@nrcan.gc.ca
Science (New York, N.Y.)
|November 8, 2005
Resumen
Los valores precisos de la constante de desintegración del lutecio-176 (176Lu) se determinaron utilizando minerales de fosfato de meteorito. Esto resuelve las discrepancias y refina la geocronología para los estudios de la evolución de la Tierra.
Área de la Ciencia:
- La geoquímica es la geoquímica.
- Cosmoquímica es la cosmoquímica.
- Las citas radiométricas.
Sus antecedentes:
- La geocronología precisa es crucial para comprender la evolución de la Tierra.
- El sistema de desintegración radiactiva de lutecio-176 (176Lu) a hafnio-176 (176Hf) es vital para esto.
- Las determinaciones anteriores de la constante de desintegración de 176Lu mostraron discrepancias entre los datos terrestres y los de meteoritos.
Objetivo del estudio:
- Para determinar con precisión la constante de decaimiento 176Lu.
- Para conciliar valores contradictorios obtenidos de minerales terrestres y meteoritos.
- Para mejorar la precisión de la geocronología de Lu-Hf.
Principales métodos:
- Análisis de datos de Lu-Hf altamente radiogénicos de minerales de fosfato.
- Utilizando minerales de fosfato de los meteoritos de Richardton (condrita ordinaria) y Acapulco (acondrita primitiva).
- Comparación con el sistema isotópico Uranio-Plomo (U-Pb) bien calibrado.
Principales resultados:
- Nuevos valores de las constantes de desintegración obtenidos de los meteoritos: 1,864 x 10^-11 +/- 0,016 x 10^-11 años^-1 (Richardton) y 1,832 x 10^-11 +/- 0,029 x 10^-11 años^-1 (Acapulco).
- Estos valores son estadísticamente idénticos a los previamente determinados a partir de minerales terrestres.
- Se logró una coherencia interna entre los datos de meteoritos y los datos de minerales terrestres.
Conclusiones:
- La constante de decaimiento 176Lu es consistente entre las muestras extraterrestres (meteoritos) y las terrestres.
- Esto resuelve discrepancias anteriores y valida el uso de la datación Lu-Hf para ambos.
- Una mayor precisión en la geocronología mejorará los modelos de la Tierra y la evolución planetaria.
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